it is physically impossible to round up and deport 12-18 million people.

We don't have to deport anyone. Cut off their ability to get a job. AZ voters passed a very strict law last year that inflicts hard core consequences for anyone, businesses or individuals to hire illegal aliens. It has had an impact. Some of the school districts in the largely hispanic areas have seen a sharp decline in enrollment. One district alone saw a decline of 1500 students in a single school year as soon as the law was passed.